1. Field of the Invention
The present invention relates to a rear projection apparatus having a screen, projection optics and an image module for production of an image which is projected by means of the projection optics from the rear onto the screen, such that a viewer who is located in front of the screen can perceive the image which is projected onto the screen. The invention also relates to a method for a rear projection apparatus such as this.
2. Description of the Related Art
In the case of rear projection apparatuses such as these, the physical depth and the foot height should be as low as possible. The physical depth can be reduced by using optics with a large image field offset. However, in this case, very large incidence angles occur on the screen which, in the case of a screen which has a transmissive Fresnel pane, must not exceed a certain incidence angle thus disadvantageously restricting the capability to minimize the physical depth. In order to achieve a reduced physical depth, the screen frequently has a reflective Fresnel pane, by means of which the necessary beam deflection is carried out on the screen. However, since the minimum incidence angle in the case of the reflective Fresnel panes must not be less than about 40°, this means that this incidence angle must be selected even at the point which is closest to the axis of the screen (viewed towards the projection optics), as a result of which the foot height is disadvantageously relatively large. Fresnel structures result in increased light losses even at angles of less than 55°.
In EP 1 452 907 A1, the Fresnel pane is partially reflective and partially transmissive, in order to minimize the foot height. However, this leads to the disadvantage that unacceptable image artifacts occur in the transitional area between the reflective area and the transmissive area of the Fresnel pane.